1. Field of the Invention
The present invention relates generally to asphalt cements and to asphalt or bituminous concrete paving compositions. More specifically, the present invention is concerned with the provision of novel reinforcing filler compositions for use in asphalt cements, which reinforcing filler compositions impart desirable properties to asphalt cements, per se, and to asphalt concretes formed therewith.
2. The Prior Art
In the 1962 Proceedings of the Australian Road Research Board, Vol. 1, Part 2, there appear separate reports by K. G. Martin (pages 895 ff) and A. G. Aliotti (pages 912 ff). The major premise upon which these reports are based resides in the authors' respective conceptualizations of benefits to be enjoyed by the use of rubber reinforcing grades of carbon black as additives in asphalt cements and concretes. Unfortunately, the experimental results of Martin's work, wherein there were employed rubber-grade carbon black pellets, led this author to the conclusion that the benefits he originally projected were either not forthcoming or existed to such a minor degree as to be of minor significance. Martin further concluded that the optimal amounts of carbon black to be employed were about 3 weight parts of carbon black on 100 weight parts of the asphalt cement. Attempts by Martin to use higher amounts of carbon black and to add higher amounts of fluxing oil separate from the carbon black resulted in the conclusion that "if an aromatic oil is used to facilitate dispersion, the fluxing effect of the oil on the bitumen more than offsets any advantages conferred by the carbon black." The Aliotti report merely provides a condensed review of the history, techniques of manufacture and properties of carbon black, the author speculating that incorporation of carbon black into asphalt cements should have some beneficial effects. However, Aliotti does not teach or suggest as to how to achieve the beneficial results; he merely submits that work should be encouraged by responsible authorities to conduct practical field tests.
In accordance with the present invention, there are now provided carbon black based reinforcing filler compositions which compositions impart profound and beneficial improvements in the properties of asphalt cements and in bituminous or asphalt concrete paving compositions formed therewith.